JPS63286436A - Production of polycarbonate granules - Google Patents

Abstract

PURPOSE:To obtain the titled useful granules economically, using a simple equipment without causing crystallization and/or pipe cloggings, by treatment while keeping the temperature of the warm water and the amounts of the components in the reaction system within each specified range. CONSTITUTION:A mixture of warm water and polycarbonate granules containing small quantities of an organic solvent is continuously fed, while stirring, with an organic solvent solution of polycarbonate, and the polycarbonate granules produced, while evaporating said solvent, are continuously discharged out of the system. During the above processes, the temperature of said warm water is kept within a range 60-80 deg.C, and the amount of the polycarbonate granules in the system maintained so as to be 25-40wt.% based on the total amount of the said granules and warm water, thus obtaining the objective granules. The granules thus obtained are porous, being easy to dehydrate and eliminate the solvent contained. When dried, said granules gives a bulk density 0.3-0.6g/cm<3> and particle size 0.1-10mm, being in a noncrystallized state.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing polycarbonate granules from a solution of polycarbonate in an organic solvent, and more specifically,
The present invention relates to a method for producing polycarbonate granules that exhibit no melting point.

<Prior Art> Many methods have already been proposed for producing polycarbonate granules from a solution of polycarbonate in an organic solvent.

That is, a method of flaking or granulating by contacting with hot water or steam, and concentration.

Known methods include gelling by cooling or adding polycarbonate powder and pulverizing the gel, and gelling by adding a non-solvent or poor solvent and pulverizing or pulverizing the gel.

Generally, polycarbonate A derived from bisphenol A is polyethylene terephthalate or nylon 6.6.
It is considered to be a polymer that is difficult to crystallize. However, when containing an organic solvent, it tends to crystallize, especially under conditions where shear forces are applied.
Many of the polycarbonate granules obtained by the above-mentioned method show distinct melting points in DSC measurements.

In the prior art, Japanese Patent Publication No. 40-3533 describes
It has been disclosed that flakes obtained by passing a solution of polycarbonate into turbulent water at 40 to 100°C, especially 90 to 100°C, are hardly crystallized; , the bulk density is 0.1g/I:ll because it has a lot of space inside.
This is extremely inconvenient in handling. As a means to avoid the formation of flakes or increase bulk density,
Publication No. 37424 discloses a method in which a polycarbonate solution is injected through pores onto or below the surface of warm water at 50 to 75°C under stirring, but the resulting solid polycarbonate is shaped like a small balloon (Japanese Patent Application Laid-Open No. Showa 59-11581
(see Publication No. 8) or become string-like, making it difficult to obtain satisfactory granules suitable for molding. Furthermore, as an improvement method for this, JP-A-59-133228 and JP-A-61-27208 propose a method in which a part of the water slurry in the granulation tank is circulated through a wet pulverizer. The equipment becomes complicated, and it is not always satisfactory because piping may become clogged between the granulation tank and the pulverizer, or crystallization may occur during the pulverization process.

<Objective of the Invention> An object of the present invention is to provide a method for obtaining polycarbonate granules in an amorphous state that does not show a melting point in DSC measurement from a polycarbonate solution in an organic solvent using a simple apparatus.

<Structure of the Invention> The present invention provides polycarbonate which is produced by continuously supplying an organic solvent solution of polycarbonate to a mixture of polycarbonate granules containing 9 organic solvents and warm water under stirring, and evaporating the solvent. In the method of continuously discharging the granules out of the system, the humidity of the hot water is maintained within a range of above 60°C and below 80°C, and the amount of polycarbonate granules in the system is controlled to A method for producing polycarbonate granules, characterized in that the amount is maintained within a range of 25 to 40% by weight based on the total weight of hot water.

The polycarbonate used in the present invention is polycarbonate A derived from bisphenol A, but with small proportions of other dihydric phenols, such as hydroquinone,
Bis(4-hydroxyphenyl)methane, 1.1-bis(4-hydroxyphenyl)ethane, 2.2-bis(4
-bitroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)hexane, 1,1-bis(4-hydroxyphenyl)cyclohexane, α,α-bis(4
-hydroxyphenyl)toluene, α,α-bis(4
-Hydroxyphenyl)ethylbenzene, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)ketone, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfone, lower alkyl substituted products of these, etc. Copolymers with which a methylene chloride solution of about 26% by weight or more gels at room temperature are also used. Also, methylene chloride is used as an organic solvent.

Lower chlorinated hydrocarbons having a boiling point of about 60° C. or lower, such as ethylene dichloride and chloroform, can be preferably used.

The organic solvent solution of polycarbonate may be prepared by dissolving polycarbonate in an organic solvent, but an organic solvent solution of polycarbonate obtained by reacting dihydric phenol and phosgene in the presence of an organic solvent is preferably used. The concentration of polycarbonate in the solution is usually about 10 to about 25% by weight.

The granulation tank used in carrying out the present invention may be of any type as long as it can sufficiently stir and mix the contents, such as a kneader.
can be preferably used.

In the present invention, a stirred solution of polycarbonate in an organic solvent is continuously supplied, and while the solvent is evaporated, the produced polycarbonate granules are continuously discharged. It is required that the hot water in the granulation tank be maintained within a humidity range of over 60°C and 80°C or less. When the temperature is below 60°C, the evaporation rate of the solvent slows down, and the polycarbonate concentration in the organic solvent solution of the supplied polycarbonate gradually increases, reaching a concentration of 26 to 60% by weight, which is said to be a suitable concentration for polycarbonate crystallization. % range becomes too long and crystallization occurs, which is not appropriate.

Further, when the temperature exceeds 80°C, the supplied organic solvent solution of polycarbonate will solidify with voids inside, and the flakes (granules) will become small balloon-like or tempura-like, which is not suitable. Humidity can be maintained by methods such as supplying hot water or steam, jacket heating, etc., but especially when supplying steam, care must be taken to avoid local heating of the contents.

In addition, it is preferable that the supply port for supplying the polycarbonate organic solvent solution to the granulation tank is such that the solution is continuously discharged from the entire surface of the supply port.
It is not necessarily necessary to reduce the size as described below. The supply port is preferably located in the upper space of the granulation tank, at a position where the discharged solution is dispersed as quickly as possible into the mixture of polycarbonate granules and hot water.

Furthermore, the amount of polycarbonate granules in the granulation tank is 2.
It is necessary to maintain it within the range of 5-40% by weight.

The supplied organic solvent solution of polycarbonate is heated by hot water and the granules, evaporates the solvent, and rapidly increases its viscosity and turns into a solid. They are torn apart and fragmented by the light friction between their bodies. Therefore, if the amount of polycarbonate granules is less than 25% by weight, the friction between the granules will be hindered by the layer of water interposed between them, and the polycarbonate stuck to the surface of the granules will solidify without being torn off, resulting in a porous structure. The polycarbonate solution that did not adhere to the granules produced small balloon-like flakes.

If it exceeds 40% by weight, the stirring and mixing of the polycarbonate granules and hot water will become uneven, resulting in uneven humidity, and the friction between the granules will become excessive, significantly reducing the distribution of the granules. The result is that it expands to Thus, a more preferred range of amounts of polycarbonate granules is greater than 30% and less than 40% by weight.

The generated polycarbonate granules and excess hot water are
It becomes a slurry and is continuously discharged from below the water surface of the mixture in the tank.

<Effects of the Invention> Since the polycarbonate granules obtained by the present invention are porous, they can be easily dehydrated and solvent removed by known methods. The dry granules thus obtained have a bulk density of 0.3 to about 0.69 and a particle size of about 0.1 to about 10 mm, but the most significant feature is that they do not have a melting point, that is, they are not crystallized. That's true. Since the polycarbonate A granules produced by the conventionally known gelling method have a melting point of about 225°C to 235°C, during melt molding, the resin humidity should be at least about 240°C.
It was necessary to keep the temperature above ℃. However, since the polycarbonate of the present invention can be melted at low temperatures, in melt blending with styrene resins, acrylic resins, etc., problems such as depolymerization of these resins can be avoided.

In addition, conventional bulky polycarbonate does not have a kneading function in powder molding such as rotary molding, so it is necessary to heat it to a higher temperature. However, since the polycarbonate granules according to the present invention are not crystallized, it is possible to reduce the resin humidity during molding by at least about 10°C. In this way, depolymerization during melt blending can be significantly reduced, and excellent industrial effects can be brought about, such as the ability to save electricity, fuel, etc. during melt molding.

<Example> The present invention will be explained in detail with reference to Examples below.

Example 1 Amorphous polycarbonate powder 1 with a bulk density of 0.5 g/ac was placed in a kneader with an internal capacity of 500Q and equipped with a solution supply port, a steam inlet, a hot water inlet, a steam outlet, and an overflow port.
00 kg and 200 kg of warm water were added and stirred. When the water temperature reaches approximately 65°C, while continuing to stir, add 1 ml of methylene chloride solution with a polycarbonate concentration of 15% by weight.
Start feeding continuously at a rate of 0/(f/min, and at the same time water vapor at a pressure of 2.7 Ky/cpA at a rate of 97 min at a rate of 1.26, and hot water at 65°C at a rate of 2.37/9/f/min. The water temperature was maintained at about 65°C, and a water slurry with a polycarbonate concentration of about 33% by weight was continuously discharged from the overflow port.The evaporated methylene chloride was transferred from the discharge port to a condenser. The water was separated from the entrained water.

Polycarbonate powder was separated from the discharged water slurry by centrifugation and dried. Bulk density is 0.51
g/CC and DSC measurement showed no melting point.

Example 2 Water temperature was approximately 75°C, and water vapor velocity was 1.31 K'J/min.

The procedure was the same as in Example 1 except that the hot water rate was changed to 2.91 K97 minutes. The bulk density of the obtained polycarbonate powder was 0.41 g/CC, and it did not show a melting point in DSC measurement.

Comparative example 1 The water temperature was approximately 55°C, and the steam rate was 1.22 9/min.

Example 1 except that the hot water rate was 2.10 Kg/min.
operated in the same way. The obtained polycarbonate powder had a bulk density of 0.639/cc and a melting point of 234° C. as measured by DSC.

Procedural amendment

Claims (1)

[Claims] An organic solvent solution of polycarbonate is continuously supplied to a mixture of polycarbonate granules containing a small amount of organic solvent and hot water under stirring, and the resulting polycarbonate granules are continuously removed from the system while the solvent is evaporated. In the method of discharging, the humidity of the hot water exceeds 60°C and
Polycarbonate granules, characterized in that the temperature is maintained within a range of 0°C or lower, and the amount of polycarbonate granules in the system is maintained within a range of 25 to 40% by weight based on the total weight of the polycarbonate granules and hot water. How the body is manufactured.